The Labour leader said that Salman Abedi’s suicide attack was the direct result of Britain’s foreign policy in the Middle East.

“Soldiers that served under me in Afghanistan have been calling me. They feel terribly betrayed and angry,” said Col Richard Kemp, who commanded British troops in Afghanistan.

“These are men and women who fought to the best of their ability in very challenging circumstances. Some paid an especially high price, surviving and returning with permanent physical and mental scars.

Jeremy Corbyn in pictures

Labour Leader Jeremy Corbyn takes part in a community meeting at the Guru Har Rai Gurdwara Sahib temple

Britain's opposition Labour Party leader Jeremy Corbyn speaks at an anti-racism rally in London

In his controversial speech Mr Corbyn confirmed that he would change British foreign policy by no longer intervening in Middle Eastern conflicts.

“We must be brave enough to admit the ‘war on terror’ is simply not working. We need a smarter way to reduce the threat from countries that nurture terrorists and generate terrorism,” he said.

General Lord Dannatt, former head of the British Army, criticised the speech as an “extraordinary intervention just three or four days after a terrorist outrage”.

He said: “As a soldier, a speech like that simply tells all those brave men and women who fought in Iraq and Afghanistan, and the families of those who did not return, that it was all a waste of time.”

He conceded that Corbyn was correct that Iraq and Afghanistan could have been better handled.

But he added that these “difficult operations” were not the failures they are being portrayed as.

“While it is not a peaceful country and never will be, Afghanistan is no longer under control of the Taliban. It is a much more stable country than it was and our intervention served a purpose,” he said.

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Diane Abbott suggested Corbyn may have met members of the IRA in their role as Sinn Fein activists

“As far as Britain’s involvement in southern Iraq is concerned, Basra has been given a chance it would never have had under Saddam Hussein.

“The 179 lives we lost there have given its inhabitants opportunity. It is very important to preserve this for veterans and the families of people who lost their lives there.”

He said the Labour leader’s plans on Britain’s future policy espoused “outdated left-wing views” that no longer fit in the modern context.

“For a country like Great Britain, one of the permanent members of the security council, a leading major power within Nato and Europe, it is very isolationist to say we are not going to get involved. There will be circumstances in the future where we will just have to get involved,” he said.

He added: “And let’s not forget that this is the man who had admitted that if he became prime minister, he would never press the nuclear button, so our nuclear deterrent would be rendered utterly useless.”

The criticism came as Jeremy Corbyn’s shadow home secretary Diane Abbott suggested the leader may have met members of the IRA in their role as Sinn Fein activists – despite Corbyn insisting on Friday that he had “never met the IRA”.

Confronted during an interview on LBC radio with reports that Mr Corbyn had shared platforms with convicted bomber Brendan McKenna and IRA member Raymond McCartney, Ms Abbott said: “He met with Sinn Fein. I think his understanding is he met with them in a capacity as activists in Sinn Fein.

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'It is increasingly clear Jeremy Corbyn will make up anything to mislead voters', says Boris Johnson

"I think we have to distinguish between conducting private meetings and supporting violent attacks and actually being on a platform.”

Ms Abbott declined to disown comments in a 1988 interview with a pro-Republican journal in which she reportedly said: “Every defeat of the British state is a victory for all of us.”

But she said the comment was made 34 years ago and that she had since “moved on”.

Foreign Secretary Boris Johnson said: “Jeremy Corbyn’s lies have been exposed by his own shadow home secretary. Just hours after Corbyn claimed he had never met the IRA, Diane Abbott says he did.

“It is increasingly clear Jeremy Corbyn will make up anything to mislead voters.”